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> Rust makes roughing out new features very hard.

> I don’t know about anyone else, but at least for me, when I’m building a new feature I usually don’t have all the data types, APIs, and other fine details worked out up front. I’m often just farting out code trying to get some basic idea working and checking whether my assumptions about how things should work are more-or-less correct. Doing this in, say, Python is extremely easy, because you can play fast and loose with things like typing and not worry if certain code paths are broken while you rough out your idea. You can go back later and make it all tidy and fix all the type errors and write all the tests.

> In Rust, this kind of “draft coding” is very difficult, because the compiler can and will complain about every goddamn thing that does not pass type and lifetime checking — as it is explicitly designed to do. This makes perfect sense when you need to build your final, production-ready implementation, but absolutely sucks when you’re trying to cruft something together to test an idea or get a basic foundation in place. The unimplemented! macro is helpful to a point, but still requires that everything typechecks up and down the stack before you can even compile.

This rings so true for me. I could "mock up" entire apps using interfaces in Java, without having to actually write impl code. I could be sloppy as hell around the edges, but that didn't matter, because I could get the large design right without the compiler screaming.

In Rust, there is the chasm between no code and anything that works, feels so draggy.